Comment 0 for bug 2025204

To backport upstream fix https://github.com/umlaeute/v4l2loopback/pull/543 for https://github.com/umlaeute/v4l2loopback/issues/448.

"Gstreamer's v4l2sink is known to submit buffers with bytesused set to the length of the buffer instead of the size of the actual image-data within the buffer which is typically smaller due to buffer sizes being rounded op to a page-size: ..."